The present invention relates to an abrasive article, such as an abrasive brush, including a binder and a plurality of abrasive particles and a method of making such an abrasive article by reaction injection molding.
Brushes have been used for many years to polish, clean and abrade a wide variety of substrates. These brush products typically have a plurality of bristles that contact the substrate. Abrasive particles can be added to bristles to increase their abrasiveness. There are many manufacturing steps necessary to manufacture a conventional abrasive brush having bristles which contain abrasive particles. A mixture of abrasive particles and a thermoplastic binder may be combined and then extruded to form a bristle. The bristle is then cut to the desired length. A plurality of these bristles are then mechanically combined to form a brush segment. Next, a plurality of these brush segments may be installed on a hub or plate to form a brush.
One example of such a brush is disclosed in U.S. Pat. No. 5,045,091 (Abrahamson et al.). In Abrahamson et al., a plurality of abrasive bristles are mechanically clamped together and a root system is installed to form a brush segment. A plurality of these brush segments are installed on a rotary hub. Another arrangement for mechanically mounting bristles on a hub to form a brush segment is disclosed in U.S. Pat. No. 5,233,719 (Young et al.). Young et al. teach a brush segment comprising a substrate with a carpet of bristles mounted on one side of the substrate, by means of a polymeric resin for example, and a root system extending from the opposite side of the substrate for engagement with a rotary hub. U.S. Pat. No. 5,400,458 (Rambosek) teaches a brush segment having a plurality of bristles embedded in a polymeric base portion. A root means for attaching the segment to a hub can be integrally molded with the base.
U.S. Pat. No. 5,233,794 (Kikutani et al.) discloses a rotary tool having a rotating tip formed integrally with a shaft. The rotary tool is formed of a thermosetting resin containing inorganic long fibers with a high degree of hardness as an abrasive means in an amount from 50% to 81% by volume. The long inorganic fibers can have a diameter in the range of 3 xcexcm to 30 xcexcm. In one of the embodiments of Kikutani et al., the rotating tip is formed as a column or cylinder with elements which correspond to the bristle of a brush extending from the tip.
U.S. Pat. Nos. 5,152,917 and 5,304,223 (Pieper et al.) teach coated abrasive articles comprising precisely shaped abrasive composites bonded to a backing. The abrasive composites comprise binder and abrasive particles. The precisely shaped composites can be in the form of, for example, pyramids, sawtooth grooves, or linear grooves. The maximum distance between corresponding points on adjacent composite shapes can be less than one millimeter. The coated abrasive of Pieper et al. can be made, for example, according to the following general procedure. First, a slurry containing abrasive grains and binder is introduced to a production tool. Second, a backing is introduced to the outer surface of the production tool such that the slurry wets the front side of the backing. Third, the binder is at least partially cured. Fourth, the production tool is removed from the backing.
U.S. Pat. Nos. 5,174,795 and 5,232,470 (Wiand) teach a planar abrasive article comprising a sheet portion with a plurality of protrusions extending therefrom. Abrasive particles are homogeneously dispersed throughout the moldable material comprising the article. Wiand teaches one embodiment having short protrusions extending 1.6 mm (0.063 in.) from the backing and having a 3.2 mm (0.125 in.) diameter, and another embodiment having short protrusions extending 1.3-1.5 mm (0.05-0.06 in.) from the backing and having a 1.3 mm (0.05 in.) diameter.
G.B. Patent Application No. 2,043,501 (Dawkins) discloses an abrasive article for polishing ophthalmic workpieces. The abrasive article is made by injection molding a mixture of abrasive grains and a thermoplastic binder to form an abrasive article comprising a flexible backing having a plurality of upstanding projections, the ends of which act as operative abrading surfaces.
U.S. Pat. No. 5,427,595 (Pihl et al.) discloses an extruded abrasive filament including a first elongate filament component having a continuous surface throughout its length and including a first hardened organic polymeric material and a second elongate filament component coterminous with the first elongate filament component, including a second hardened organic polymeric material in melt fusion adherent contact with the first elongate filament component along the continuous surface. The second hardened organic polymeric material can be the same or different than the first hardened organic polymeric material. At least one of the first and second hardened organic polymeric materials includes a thermoplastic elastomer having abrasive particles adhered therein. Also disclosed is an abrasive article comprised of at least one abrasive filament mounted to a substrate such as a hub adapted to be rotated at high speed.
Polyamide, also known as xe2x80x9cnylonxe2x80x9d, filaments were developed in the late 1950""s as a synthetic alternative to natural filaments. At about that time an extrusion process was developed for dispersing abrasive particles uniformly in a nylon matrix in the form of a filament (U.S. Pat. Nos. 3,522,342 and 3,947,169). A review of polyamide abrasive filaments is presented by Watts, J. H., xe2x80x9cAbrasive Monofilaments-Critical Factors that Affect Brush Tool Performancexe2x80x9d, Society of Manufacturing Engineers Technical Paper, 1988, a written version of a presentation by the author at the WESTEC Conference, held Mar. 21-24, 1988. It is known to use conventional inorganic abrasive particles with such polyamide filaments. As explained by Watts, as filaments of this type wear, new abrasive particles are exposed. An abrasive filament brush tool made using a plurality of these filaments is thus regenerated during use. While adequate for many purposes, various polyamides have property limitations which make their use less than optimal for certain applications of abrasive filaments.
U.S. Pat. No. 5,460,883, (Barber, Jr., et al.) describes the use of thermoplastic elastomers in abrasive filaments to reduce or overcome such limitations of polyamide filaments.
An abrasive brush and filaments are described in International Publication No. WO 96/33638 (Johnson et al.), published on Oct. 31, 1996. Johnson et al. report that moldable polymers can be used in brushes, brush segments and filaments. Preferably, the moldable polymer is an organic binder material that is capable of being molded, i.e., it is capable of deforming under heat to form a desired shape. Johnson et al. teach that desirable moldable polymers may be a thermoplastic polymer, a thermosetting polymer, a thermoplastic elastomer, and mixtures thereof. Johnson et al. also teach that thermoplastic elastomers may be used in processes such as injection molding, extrusion, blow molding, and the like. Injection molding, as taught by Johnson et al., provides placing a mixture of pellets including a moldable polymer and, optionally, abrasive particles in a hopper which feeds the mixture into a first or rear side of a screw injector. The softened mixture is then passed into a mold, wherein the screw injector includes a heated barrel for melting the mixture, while a rotating screw within the barrel propels the mixture into the mold. Thus, as described by Johnson et al., injection molding utilizes a single moldable polymer source from which to feed the screw injector and, subsequently, the mold.
There is a need to provide an abrasive article, such as an abrasive brush, that is easily, rapidly, and inexpensively manufactured. An abrasive article so manufactured preferably provides suitable durability and abrading characteristics. There is also a need to provide an abrasive brush having abrasive particles that can remove foreign material from a workpiece surface efficiently without damage to the workpiece surface, or that is capable of providing a desired finish to the workpiece surface.
One aspect of the present invention is a method for making an abrasive article that is easy, fast, and inexpensive, and which provides a suitable abrasive article that is sufficiently durable and possesses acceptable abrading characteristics. Preferably, a method for making an abrasive article includes supplying an effective amount of abrasive particles to at least a portion of an abrasive article mold, wherein the abrasive article mold comprises a plurality of bristle segment portions; supplying a binder precursor matrix to the abrasive article mold, wherein the binder precursor matrix comprises at least two interactive components capable of forming a binder selected from the group consisting of a polyurethane/urea binder and an epoxy binder; and allowing the binder precursor matrix to cure within the abrasive article mold such that the abrasive particles are secured within a binder formed from the binder precursor matrix. More preferably, the method according to the invention includes reaction injection molding or RIM.
As used herein, xe2x80x9can effective amount of abrasive particlesxe2x80x9d refers to that amount of abrasive particles added during a method of making an abrasive article such that the resulting abrasive brush can remove foreign material from a workpiece surface efficiently without damage to the workpiece surface, or is capable of providing a desired finish to the workpiece surface.
As used herein, xe2x80x9cRIMxe2x80x9d refers to reaction injection molding that relates to a production method that includes mixing and reacting one or more, preferably two or more, chemical components to form a solid structure. Preferably, the two or more chemical components are supplied as interactive liquid components. As used herein, xe2x80x9cRIMxe2x80x9d also refers to and includes RRIM and SRIM. xe2x80x9cRRIMxe2x80x9d generally refers to reinforced reaction injection molding wherein fillers are typically added to at least one of the interactive chemical components. Fillers generally include such materials as milled glass, chopped glass, and flake glass. xe2x80x9cSRIMxe2x80x9d generally refers to structural reaction injection molding that typically includes reinforcing materials, such as glass fiber preform, in the mold where the chemical components are injected to solidify around the preform.
As used herein, xe2x80x9cinteractivexe2x80x9d means that the components of the binder precursor matrix undergo a mechanism with each other such as covalent bonding, hydrogen bonding, ionic bonding, van der Waals"" forces, and the like, that may result in crosslinking and/or chain extending of the components.
As used herein, xe2x80x9ccure timexe2x80x9d refers to a period of time required for a complete interaction to take place between the components of the binder precursor matrix such that the physical nature of the matrix irreversibly changes to form a binder. For example, the physical state of the binder precursor matrix may change to another state to form the binder, such as from a substantially liquid state to a substantially solid state.
A method in accordance with the present invention preferably includes supplying the binder precursor matrix to the abrasive article mold by supplying each of the at least two interactive components separately to a mixer prior to supplying the binder precursor matrix to the abrasive article mold.
In one embodiment, the binder precursor matrix forms a polyurethane/urea binder having a soft segment to hard segment ratio of about 10:1 to about 1:2. Preferably, the binder precursor matrix includes a first component selected from the group consisting of an amine, a polyol, or a mixture thereof, wherein the first component has an average amine and/or hydroxy functionality of at least about 2 and an equivalent weight of at least about 30 grams and less than about 10,000 grams per equivalent; and a second component comprising a polyfunctional isocyanate having an average isocyanate functionality of at least 2 and an equivalent weight of at least about 80 grams and less than about 5000 grams per equivalent. The binder precursor matrix may further include a chain extender.
In another embodiment, the binder precursor matrix includes a first component comprising a glycidyl ether expoxide group containing material. and a second component comprising an amino-terminated aliphatic polyether curing agent. The binder precursor matrix may further include a polymeric toughening agent having both a rubbery phase and a thermoplastic phase or being capable of forming, with the epoxide group containing material, both a rubbery phase and a thermoset phase on curing; and a catalyst capable of providing an exotherm of at least about 20xc2x0 C.
Preferably, supplying a plurality of abrasive particles to an abrasive article mold includes filling the abrasive particles in at least some of the plurality of bristle segment portions of the mold. More preferably, the step of supplying a plurality of abrasive particles to at least a portion of an abrasive article mold includes filling at least about 50% by volume to at least some of a plurality of bristle segment portions of the mold with abrasive particles.
In accordance with the present invention, the step of supplying a binder precursor matrix to the abrasive article mold typically occurs after the step of supplying a plurality of abrasive particles to at least a portion of an abrasive article mold.
The method may also include adding an optional additive to the binder precursor matrix, wherein the optional additive is preferably selected from the group consisting of a filler, a fiber, an antistatic agent, an antioxidant, a catalyst, a processing aid, a dessicant, a UV stabilizer, a flame retardant, a lubricant, a wetting agent, a surfactant, a pigment, a dye, a coupling agent, a plasticizer, a suspending agent, and combinations thereof.
Another aspect of the present invention provides an abrasive article produced by the method described above, wherein a plurality of bristles of the abrasive article includes a binder formed from the binder precursor matrix and a plurality of abrasive particles adhered together within the binder, wherein the binder and the plurality of abrasive particles are in a ratio of about 1:3 or more by weight.
Another aspect of the present invention provides a method for making an abrasive article that includes filling a plurality of abrasive particles to about a 50% by volume of at least a portion of a plurality of bristle segments of an abrasive article mold. The method also includes supplying a binder precursor matrix comprising at least two interactive components to the abrasive article mold, wherein a first component is selected from the group consisting of a polyurea or polyurethane/urea which results from the polymerization of a polyfunctional amine having functionality of at least 2 and an equivalent weight of at least about 300 and a polyfunctional isocyanate prepolymer having functionality of at least 2 and an equivalent weight of at least about 300; and a second component is selected from the group consisting of a polymerized polyfunctional isocyanate or polyfunctional amine having a functionality of at least about 2 and equivalent weight of less than about 300; and allowing the binder precursor matrix to cure within the abrasive article mold such that the abrasive particles are secured within a binder formed from the binder precursor matrix, wherein the binder includes a soft segment to hard segment ratio of about 10:1 to about 1:2.
A further aspect of the present invention provides a method for making an abrasive article that includes filling a plurality of abrasive particles to about a 50% by volume of at least a portion of a plurality of bristle segments of an abrasive article mold. The method also includes supplying a binder precursor matrix comprising at least two interactive components to the abrasive article mold, wherein a first component comprises a glycidyl ether monomer of the formula: 
where R1 is alkyl or aryl and m is an integer from 1 to 6; and a second component comprising a polyether diamine having the formula
H2Nxe2x80x94R2O"Parenopenst"R3O"Parenclosest"nR2xe2x80x94NH2
wherein R2 is a straight or branched chain alkylene group having 2 to 4 carbon atoms, R3 is an hydrocarbolene group having 2 to 8 carbon atoms selected from straight and branched chain alkylene groups having 2 to 4 carbon atoms, cycloalkylene groups having 4 to 8 carbon atoms, and arene groups having 6 to 8 carbon atoms, and n is an integer from 1 to 10 such that the average molecular weight of the compound is from about 175 to about 750; and allowing the binder precursor matrix to cure within the abrasive article mold such that the abrasive particles are secured within a binder formed from the binder precursor matrix, wherein the binder and the plurality of abrasive particles are in a ratio of about 1:3 or more by weight.
Yet another aspect of the present invention provides an integrally molded abrasive article that includes a generally planar base having a first side and a second side; a plurality of bristles integrally molded with and extending from the first side of the base; wherein: the base comprises a binder formed from a binder precursor matrix comprising at least two interactive components and is essentially free of abrasive particles; and at least a portion of the plurality of bristles comprise a plurality of abrasive particles adhered within the binder such that the ratio of binder to abrasive particles is at least about 1:3 by weight. Preferably, the binder is selected from a polyurethane/urea binder or an epoxy binder. The plurality of abrasive particles preferably include a material selected from an inorganic material, an organic material, or an agglomerate thereof. The integrally molded abrasive article may further include an attachment constituent on the second side of the base.